Construction of simplified impedance model based on electrochemical mechanism and identification of mechanism parameters

On the basis of the three-scale impedance model, this article establishes a simplified impedance model corresponding to the mechanism of the pseudo two dimensions (P2D) model. The simplified impedance model aims to strike a balance between simplicity, accuracy, and mechanism. It includes the Faraday process of electrochemical reactions, the non-Faraday process of double layer capacitance dispersion effect, and the mass transfer process in solid and solution phases. We validate the simplified impedance model using electrochemical impedance spectroscopy (EIS) data at frequencies ranging from 0.1 Hz to 1 kHz at five different SOC levels. By substituting the mechanism parameters obtained from the simplified impedance model identification into the P2D model, the accuracy and mechanism of the simplified impedance model were verified under constant current charging and discharging conditions at different rates and under Federal Urban Driving Plan (FUDS) conditions. The simplified impedance model provides feasibility for identifying the parameters of the lithium battery mechanism model based on electrochemical impedance spectroscopy data, especially for the difficult to identify double-layer capacitors and reaction rate constants. The precise mapping relationship between the impedance model and the P2D model also lays the foundation for predicting the dynamics and aging of lithium batteries.